This application relates to the field of control of hydraulic and pneumatic apparatus, and the feedback of position and effort exerted by hydraulic apparatus to an operator of such apparatus.
Hydraulic and pneumatic powered machines require some means of translating the physical input of an operator into movement of the various members of the machine. Traditionally an operator manipulates the individual members of such a machine using some device (a manipulator) to operate directional valves that supply power to actuators that move each movable member comprising the machine. In the simplest of equipment, an operator is provided with a lever that is connected to a 4 way valve, one such assembly for every axis of motion the machine affords. Pushing or pulling a given lever moves a given machine member about its axis. The operator can also move the levers in sets or multiples to move more than one of the machine members simultaneously about their various axes. Generally, an operator visually inspects the machine to determine the position of the machine members (machine configuration). Feedback to the operator using such a scheme is limited to visual inspection of the machine and what the machine""s performance and the operator""s experience and his other senses impart to him regarding the conditions of load and resistance during any operation. Furthermore, in the simplest form of control, as the number of axes of movement are multiplied, the ability of the operator to visually inspect the response of the machine to his input and to manipulate multiple valves to move simultaneously about multiple axis becomes increasingly taxed. One example of such complexity is found in machines which are anthropomorphic (a machine the members of which are capable of the same range of motion as an analogous human anatomical feature such as a hand and arm). For a machine to duplicate the range of motion of a human hand and arm would require at least 27 axes of motion, which is probably beyond the ability of even the most skilled operator to operate smoothly if presented with a single lever control for every axis of motion.
Some schemes have been advanced wherein an operator inputs movement to a machine using a manipulator that is designed such that it breaks down the natural movement of the operator""s input into motion of multiple machine members along multiple axis and transmits signals activating hydraulic cylinders to move a collection of machine members along a path that corresponds to the operator""s movement applied to the manipulator. In such schemes the manipulator performs two functions, one function is to permit the machine to be operated by the use of xe2x80x9cnaturalxe2x80x9d or xe2x80x9cintuitivexe2x80x9d motions, that is controlled without the operator having to translate a desired motion into a series of lever manipulations, and the second function is that it limits the operator""s movements to those motions that can be carried out by the machine interfaced to the manipulator. Thus, when manipulating machines that are not anthropomorphic, the manipulator constrains the natural movements of the operator to those which the associated machine can execute while providing the operator with an intuitive interface to the machine.
When manipulating more complex machinery a manipulator provides a method of utilizing intuitive or natural operator movements to control simultaneous motion of a plethera of machine members which would not be feasible to control using simple control schemes. These two aspects of a manipulator make it possible for an operator of lesser training to smoothly operate reasonably simple machinery using intuitive input movements, and at the same time make it possible for an operator of any skill level to control a machine with a larger number of machine members operating about a larger number of axes, than would otherwise be feasible.
One central-advantage of using such a manipulator to control a machine, regardless of the complexity of the machine or skill of the operator is that an operator does not have to mentally translate the motion he or she desires the machine member to make into a movement of several control levers, but has only to move the manipulator in a scale duplicate motion of the one the operator desires the machine to perform. One difficulty inherent in using natural motion lies in the fact that uncontrolled motion can lead to dangerous operating conditions in the vicinity of the machine executing an uncontrolled operator command. An operator requires position and force feedback to operate hydraulically and pneumatically powered equipment safely, particularly if the equipment being operated is much larger or smaller in size than the operator.
The prior art includes a number of schemes that provide load sensing along with positional and rate feedback using pressure and position sensors, differential amplifiers, and torque motors. These devices are employed to effect a system in which the application of hydraulic power to the drive device moving a related machine member is varied depending upon the degree in positional difference between the control element and its corresponding machine member, and the back pressure generated by the torque motors against the control elements varies with the operating pressure supplied to the drive devices.
Prior art systems which have been disclosed to help an operator with visual feedback follow. One such scheme is disclosed in U.S. Pat. No. 5,000,650 to Brewer et. al wherein a system of proximity switches and proximity targets is used to determine the position of machine members in machines comprised of jointed, movable members. The proximity switches are electrically connected to suitable devices to automatically cancel operator input to a control valve which has actuated a machine member once the machine member has reached a particular travel limit. No scheme of feedback to the operator of the control members is disclosed.
Several examples exist wherein complex motions can be input on multiple axis manipulators without the necessity of manipulating a multiplicity of input controls. One example of such a scheme is disclosed in U.S. Pat. No. 5,019,761, a manipulator arm with 6 degrees of freedom is disclosed for one handed manipulation of excavation tools having 6 axis of motion. It is claimed that this type of manipulator can be employed with any control and feedback scheme known in the prior art. No specific methods of control and feedback are disclosed.
In U.S. Pat. No. 5,002,454 to Hadank et.al. there is disclosed a configuration of multiple axis control levers which generate electrical signals in response to operator hand movements that are said to provide a more intuitive operation of equipment having multiple axis machine members. No specific scheme of converting the electrical signals into operation of the machine members is disclosed and no scheme of feedback to the control levers is disclosed.
U.S. Pat. No. 3,880,304 to Strickland discloses a system of valve actuating elements mounted on a scale model representation of a digging apparatus. The digging apparatus is comprised of a dipper, a dipper arm, and a crowd arm mounted on a rotating base (to use the descriptive language of the ""304 patent). The valve actuating elements each ultimately control a hydraulic directional control valve that supplies hydraulic pressure to a hydraulic actuator which in turn moves one of the members of the digging apparatus. The components of the scale model are mechanically linked by a system of cables, chain drives, and levers to the components of the digging apparatus which they model in such a manner that the motion of the digging apparatus is transmitted to the scale model components. In this manner, the configuration of the digging apparatus is mapped onto the model components, giving a visual readout of the configuration of the digging apparatus to an operator. A system of control knobs and levers is arranged about the scale model of the digging apparatus such that by moving them a lever member is brought to bear on the valve actuating element mounted on the scale model that controls the identical motion in the digging apparatus. Thus moved, the lever member activates the associated valve actuating element, in turn operating the control valve which directs hydraulic fluid into the driving mechanisms associated with the related member of the digging apparatus. A system of pins act as stops which prevent the operator from moving a control lever more than enough to activate the related control valve actuator. Because of the mechanical connection (pulleys, levers, cables) of the scale model to the actual members of the digging apparatus, as the actual members of the digging apparatus are moved, the scale model and thus the control levers mounted on it will move to a correspondingly scaled degree. While this system provides a visual feedback to the operator as to the configuration of the digging apparatus and provides the operator with a sense of the rate at which the digging apparatus is being operated, no feedback of the effort exerted by the system or the resistance of the load being moved is available to the operator from the disclosed system.
U.S. Pat. No. 5,497,568 to Strickland discloses a control system which is adaptable to the portion of the apparatus disclosed in U.S. Pat. No. 3,880,304 that activates hydraulic actuators driving the components of a digging apparatus. This control system employs the same concept of having an operator manipulate levers which are mounted on a scale model of the digging apparatus that in turn activate devices that ultimately direct hydraulic power to actuators powering the various elements of the digging apparatus. Instead of the system of cables, levers, chains, and sprockets employed in the previous patent to link the digging apparatus components and the corresponding components of the model of the digging apparatus, this patent employs hydraulic pumps to supply operating fluid to actuators on the model. The pumps are operated by the hydraulic fluid supplied to the digging apparatus actuators. The output pressure of these hydraulic pumps is directed to actuators that move the related components of the scale model an amount that corresponds to the motion of the digging apparatus. The ratio of the volume of fluid driving the hydraulic pump to the volume of fluid output by the pump is set to reflect the ratio of the volume of the digging apparatus component actuator to the corresponding digging apparatus model component actuator, making motion of a digging apparatus component be reflected in an identical scale motion of the corresponding digging apparatus model component. The disclosed apparatus operates the scale model components with a force which far exceeds the strength of the human operator. Thus, in the apparatus disclosed in the ""568 patent, like the apparatus disclosed in the ""304 patent, the operator is provided with visual feedback of the digging apparatus configuration which he can alter with an intuitive 3 axis motion, and feedback as to the rate at which the digging apparatus components are moving. No provision is made in the disclosed apparatus to provide the operator with tactile feedback that is within the ability of the human operator to discern that is proportional to that being exerted by the digging machine. Neither is the effort being applied by the digging apparatus communicated to the operator if the apparatus is stalled during an operation.
U.S. Pat. No. 4,394,102 to Batchelder et al discloses an apparatus in which a double acting control cylinder has each chamber connected to one of the two control ports of a pilot valve. The pilot valve is in turn connected to a second double acting cylinder, a pilot cylinder, such that moving the control cylinder operates the pilot valve, which in turn connects one of the chambers of the pilot cylinder to a source of hydraulic power and the other to a pressure relief valve, causing the pilot cylinder to move. The pilot cylinder is in turn mechanically connected to a 4 way control valve. Moving the pilot cylinder actuates the four way control valve which in turn supplies power to a drive cylinder, moving a machine member. A double acting feedback cylinder is fastened to either the drive cylinder piston rod or the machine member. The feedback cylinder is moved correspondingly by the movement of the machine member. The two chambers of the feedback cylinder are connected to the control ports of the pilot valve in such a manner that as the machine member is moved and correspondingly hydraulic fluid is expelled from one chamber of the feedback cylinder and drawn into the other, the fluid acting on the pilot valve control ports is moved in the same manner, causing the pilot valve to return to its neutral position. This in turn permits fluid to flow out of the full chamber of the pilot cylinder and into the empty chamber of the pilot cylinder, returning the control valve to center and discontinuing the application of power to the drive cylinder. Thus it follows that upon movement of the control cylinder, the machine element is correspondingly moved by an amount scaled to movement of the control cylinder and then stopped at that point. This patent further discloses a method of using this control system in multi-axis control devices, and in particular illustrates the use of a scale model digging apparatus fitted with the necessary control components to control a full scale digging apparatus. The disclosed control system when mounted on a scale model of the equipment it is controlling can be used to input desired motions to the equipment being controlled. The system does not provide feedback to the operator regarding the actual configuration of the controlled machine members, it is designed to shut off when the controlled machine members have moved to positions correspondingly in scale to the motion input to the model. Additionally no method is disclosed to provide the operator with feedback regarding the speed at which the controlled machine members are moving nor the force being exerted by the controlled machine members.
Several prior art schemes utilizing a separate driver to exert force against an operator""s input are disclosed in the following examples. In U.S. Pat. Nos. 5,018,922 and 4,893,981 both to Yoshinada et al, there is disclosed a control device in which sensors measure the relative positions of a control lever and a machine member, the relative rates of motion of the control level and the machine member, and the load experienced by the driver driving a machine member. Various schemes are disclosed which utilize this data to actuate a control valve supplying power to the machine member driver and to drive a torque motor which exerts a variable reverse torque against the direction in which the control lever is actuated by the operator.
Finally, U.S. Pat. No. 4,516,894 to Stolpp discloses a multiple axis control arm used to control the motion of hydraulically driven machine members that uses electrically controlled valves to route hydraulic power to the driver devices. The ""894 patent discloses that an electric signal arises in response to a detection of a difference in position between a control arm and the corresponding machine member, but does not disclose the means of detecting positional differences nor how the signal is employed to operate the associated control valves. An additional feature disclosed is the use of hydraulic drivers to work against all degrees of motion of the control arm in response to the resistance experienced by the machine members while they are moving. This system uses a variable orifice valve to direct the fluid pressure in the machine member drivers to a corresponding driver acting against a member of the control arm. A piston arrangement balances a reference pressure against the driver line pressure. As the line pressure exceeds the reference pressure, the resulting piston movement opens a control edge that admits fluid at the line pressure until the back pressure rises sufficiently to balance the pressures out, returning the piston to its former location. Admitting machine member driver line pressure increases the pressure in the driver acting against the control arm member, increasing the resistance felt in that member by the operator. In this manner this scheme also employs separate pathways to input operator commands into the machine and send feedback regarding machine operation to the operator.
As was disclosed above, a manipulator must provide a member with a separate axis of motion for each dimension in which input by moving an anatomical feature of a human operator is desired to be utilized to control a machine member. For example, a machine which duplicates the motion available to the upper arm and forearm of a normal human operator would require 5 axes of input. Increasing the number of anatomical features that can be used to input control movement to a machine quickly complicates the number of axes through which a manipulator must accommodate motion. Any one of the above prior art schemes becomes increasingly difficult to execute as each axis is added. Additionally, the scale of the equipment required to carry out these schemes makes miniaturization of the control device (manipulator) difficult when a large number of axes of movement are required. Finally, particularly if a large number of axes are required, tactile feedback to the operator in response to control input is required if an operator is to keep track of the position of the machine and the effort it is exerting, and the speed at which it is operating in response to an operator input.
One of the drawbacks of the various prior art schemes utilizing electro-hydraulic control of machinery is that even with the feedback schemes disclosed, the operator is capable of operating in a xe2x80x9cfeed forwardxe2x80x9d mode, where the torque motor supplying xe2x80x9cfeedbackxe2x80x9d or the feed back loop sampling the feedback driver can be overpowered so that the input control is considerably in advance of the actual position of the machine member being controlled. This leaves the operator in possession of some knowledge of how hard the machine is working but doesn""t give real time information regarding the configuration of the machine. This can lead to dangerous or uncontrolled and unintended movement of a machine member.
Secondly, with the connection between the operator and the machine dependent upon electrical sensing, hysteresis in the sensing components, and mechanical looseness in the system can cause the controlled machine element to effect a xe2x80x9cpalsyxe2x80x9d in its operation, making fine control of the system difficult. Finally, manipulators which offer tactile positional and force feedback for multi-axis machinery must use compact components, small volumes and short plumbing paths. If these considerations are not taken into account in construction of a manipulator, as the number of axis being controlled increases they become too large to be manipulated by an operator, and the response time becomes too slow to be of practical value.
A scheme utilizing a closed hydraulic loop to link a master control cylinder and the related machine member under the control of the master cylinder would eliminate the lack of positional feedback inherent in many systems. A scheme delivering a back pressure proportional to the effort being exerted by the machine member under control to a control input device (a lever or fitment interfaced to an anatomical feature) through the same input lines that are utilized to transmit control information to the machine member being controlled would eliminate the uncertainty exhibited by schemes in which feedback is decoupled from the input device supplying control signals. Finally, a scheme which utilized a minimum of components in the construction of a manipulator (operator input device) would permit making a manipulator that can provide for a large number of axis of movement and still be of a size and weight that it could be fixed to the anatomical features of a human operator. Such a manipulator would permit an operator to control machines having a greater number of independent axis of motion than is now practical. As well it would afford operator control of simple machines using motions more natural or instinctive to the motion which an operator desires the machine to execute. It also affords a control scheme that permits a human operator to control machines which more nearly duplicate natural human motions carried out by limbs and digits secured to such a manipulator than is possible with the present devices.
One embodiment of the present invention utilizes multiple light weight miniature hydraulic cylinders fastened to the moving members of an operators manipulator chassis. Each miniature cylinder operates as an element in a separate closed loop hydraulic system to input operator movement over multiple axis to a series of fluid based feedback/driver control modules, and receives feedback from the feedback/driver control module proportional to the effort exerted by that particular machine member. The feedback/driver control module has a minimum of components, most of which can be mounted off of the manipulator chassis. It will be appreciated by one skilled in the art that the present invention can be equally well practiced utilizing other hydraulic elements than miniature cylinders to drive the closed loop system without departing from the scope of the present invention.
As a further refinement over other schemes, the present invention utilizes the position of the machine elements under control and the line pressure of the fluid used to power the drivers of those machine elements to deliver resistance to the closed loop hydraulic input system, resulting in an input control that follows the position of the controlled machine member and feeds back a resistance to the operators motion that is adjustably proportional to the effort exerted by the controlled machine member.
The present invention also has provision for delivering a signal actuating a valve delivering power to the driver moving the machine member under control that is proportional to the effort that the operator is exerting against the feedback system, thus, by employing a proportional valve receiving this signal, hydraulic power can be supplied to a related machine member driver at a rate that is proportional to the driver""s input.
While this section discloses aspects of the present invention that may be features of various embodiments, it is neither an exhaustive list of the aspects of the invention nor is it meant to imply that all embodiments will manifest all of the disclosed aspects. A given embodiment may manifest less than all or more than all of these aspects without departing from the scope of the present invention.
One aspect of the present invention is to provide an operator of hydraulically powered equipment with a control device (manipulator) which permits control of the hydraulically powered equipment using motions natural to elements of the human anatomy.
Another aspect of the present invention is to provide a method of manipulating hydraulically powered equipment using movement which is within the scope of common human eye/hand coordination.
Another aspect of the present invention is to provide a method of giving real time tactile feedback to an operator of a machine having members driven by hydraulic power which is proportional to the position, rate of motion, and degree of effort being executed by the members of a hydraulic machine.
Another aspect of the present invention is to provide a method of providing a range of tactile feedback that is scalable to various load conditions being subject to operator control.
Another aspect of the present invention is to provide a manipulator device wherein the input members of the manipulator spatially follow rather than anticipate the position of the machine member under manipulator control.
Another aspect of the present invention is to utilize the same hydraulic control circuit used to initiate movement of a controlled machine member to provide the operator of that hydraulic control circuit with feedback regarding force and position of the controlled machine member.
Another aspect of the present invention is to provide a manipulator which can provide control of a machine with a plethora of independent axes of motion using natural human movement to input movement commands to the machine.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.